Process for the purification of blue vat dyestuffs



Patented Aug. 22, 1933 UNITED STATES PATENT OFFICE Paul Nawiasky,Ludwigshafen on the Rhine, Germany, assignor to General Aniline WorksInc., New York, N. Y.,

ware

a Corporation of Dela- No Drawing. Application March 28, 1929, SerialNo. 350,811, and in Germany April 7, 1928 1 Claim.

The present invention relates to the purification of greenish blue toblue vat dyestuffs fast to chlorine.

It is known that by fusion with caustic alkali of Z-aminoanthraquinone ablue vat dyestuif is obtained, the essential constituent of which is N-dihydro- 1.2.1 .2 -anthraquinoneazine. However, by most methods ofproduction, a product is obtained which is not pure and containsconstituents impairing the properties of the product by reducing itsfastness to chlorine.

Attempts have already been made to overcome this drawback. Thus, in theU. S. Patent No. 1,541,156 it has been suggested to produce N-dihydro-1.2.1..2-anthraquinoneazine fast to chlorine, either by fusingpure B-aminoanthraquinone with caustic alkali metal hydroxide, or elseby starting, with impure fl-amincanthraquinone and eliminating, duringthe alkali melt, the impuritieswhich cause the imperfect fastness tochlorine, by prolonging the duration of the melt or, instead ofdestroying them during the alkalimelt, eliminating them from thefinished dyestuff by a repeated alkali melt, or by one or morefractional precipitations from sulphuric acid, and the like. Since thedestruction or elimination of the impurities in this manner is alwaysaccompanied by the destruction or elimination of larger or smalleramounts of the valuable dyestuff fast to chlorine, the said process isaccompanied by losses of the desired N-dihydro-1.2.1.2'anthraquinoneazine. v Ihave now found that N-dihydro-1.2.l'.2'-'anthraquinoneazine can be produced on an inrlustrial scale with thesame purity and fastness to chlorine as by the aforesaid processaccording to the U. S. Patent No. 1,541,156 and in a substantially moreadvantageous manner, by treating N-dihydro1.2.1f. -anthraquinon eazinewhich is not fast to chlorine, with manganese dioxide, or otheroxidizing agents having a similar action, in the presence of sulphuricacid. Suitable oxidizing agents are, for example, all higher oxides ofmanganese than manganous oxide MnO. The sulphuric acid used may containa moderate amount of water, such as 15 per cent or less, but

may also use with the same result ordinary commercial concentratedsulphuric acid having a content of about 96 per cent of sulphuric acid,or acid free from water, such as sulphuric acid monohydrate, or evenWeak oleum, up to oleum containing 25 per cent of S03. All sulphuricacids of a concentration within the said limits are tobe regarded asequivalents for the purposes of the present invention, and I shalltherefore here- Whereas the N-dihydro-1.2.l.2-anthraquinone- 'azine isleft practically unaffected.

The aforesaid process is applicable to any kind of impureN-dihydro-1.2.1.2-anthraquinoneazine and is particularly suitable forthe treatment of the mixture of dyestuffs obtained by the alkali fusionof p-aminoanthraquinone in the presence of certain additions, asspecified for example in the U. S. Patent No. 746,784 and otherpatentswell-known to those familiar with the said reaction. It is notnecessary to previously separate the dyestuff B and the otheraccompanying substances as referred to in theU. S. Patent No. 724,789.According to the amount and the quality of the manganese dioxideemployed and the duration and temperature of the reaction, a veryvaluable dyestuff is obtained which, as regards purity, practicallycorresponds to the dyestuii' A of the aforesaid U. S. Patent No.724,789. r g

The purity of the final product can be still further improved bychoosing energetic conditions in the production of the crude dyestufimixture, for example, by lengthening the duration of the fusion, or bypassing over air during the fusion, and in this manner part of theimpurities ordinarily present is decomposed in the fusion.

The process according to my present invention subjecting the easilyaccessible 3.3-dimethyl-N- dihydro-1.2.1.2'-anthraquinoneazine to thedescribed treatment the fastness to chlorine and the purity are improvedand the shade becomes .more greenish. not more than about 33 per cent ofwater; we

The dyestuffs obtained according to my invention first in the form ofthe azines can be reduced in the manner already known to N-dihydro-1.2.1.2'-anthraquinoneazines, for example, by dissolving in sulphuricacid and reducing by means of phenols. Moreoventhis reduction can becarried out together with the purification in one operation.

In the same'way also sulphonic acids of N-dihydro-1.2.1.2-anthraquinoneazine and in particular the greenish-bluedyestufi obtainable according to the process of the U. S. Patent No.970,878 which is considered to be an impure sulphonic acid derived fromN-dihydro-1.2.1.2-anthraquinoneazine can be subjected to this process.Thereby purer products are obtained the dyeings of which on cotton nolonger change to yellow green or yellow when treated with chlorine. Thetreatment with oxidizing agents may be combined in one operation withthe manufacture of the sulphonic acid which serves as the initialmaterial, and, if desired, the yellowish sulphonic acid formed which isin the azine form may be converted into the hydroazine form by treatmentwith reducing agents, for example, with phenols in solution in sulphuricacid. 7

The pure sulphonic acids thus obtainable can also be prepared bytreating pure N-dihydro- 1.2.1.2-anthraquinoneazine fast to chlorine,such as is obtainable by the process according to the U..S. Patent No:1,541,156 or by the process hereinbefore described with mildsulphonating agents, preferably in the presence of boric acid.

By the term mild sulphonating agent I mean milder sulphonating agentsthan fuming sulphuric acid with a high content in S03, such as forexample oleum with 10 per cent of S03, sulphuric acid monohydrate orordinary commercial concentrated sulphuric acid. 7

Thepure sulphonic acids obtainable as afore described and also theproducts obtainable by the process of the U. S. Patent No. 948,204(which process consists in heating crude N-dihydro-1.2.1.2'-anthraquinoneazine with mild sulphonating agents preferably inthe presence of boric acid) have the disadvantage of giving dyeings oncotton from the vat which have only moderate depth of color. I havefound that this difficulty can be overcome and that valuable blue vatdyestuffs which have extremely valuable properties in the dyeing andprinting industries, in particular valuable color tones, good fastnessto light and good strength are obtained when the said sulphonic acidsare mixed with N-dihydro-1.2.1'.2- anthraquinoneazine or substitutionproducts thereof. It is preferable to employ N-dihydro- 10 parts oftechnically pure N-dihydro-1.2.1'.2'- anthraquinoneazine are dissolvedin 176 parts of sulphuric acid of 96 per cent strength and 24 parts ofwater are added, so that, finally, the water content of the sulphuricacid is about 15 per cent. A suspension of 15 parts of artificialmanganese dioxide in 180 parts of sulphuric acid of 85 per cent strengthprepared at a temperature below 45 C. is then rapidly added at atemperature below C. The mixture is then slowly raised to to C. and isstirred at that temperature for several hours, until no furtherpurification of the dyestuff occursfTh'e red-brown to orange suspensionis then poured into 1500 parts of water,

then a suspension of 20 parts of artificial treated with an addition of200 parts of a solution of sodium bisulphite, of approximately 38 to 39Baum density and heated to boiling for about half an hour, theoriginally brown yellow suspension turning blue. After filtration andwashing until neutral, the dyestuff is made into a paste which givesdyeings that are substantially purer and faster to chlorine, than thoseof the N- diphydro-1.2.1.2'anthraquinoneazine employed as the startingmaterial.

When it is desired to obtain the dyestuff in a particularly finelydivided state and in the form of the blue hydroazine, the reactionmixture is not directly poured into water, but 100 parts of fumingsulphuric acid containing 23 per cent of SO: are added whereby most ofthe dyestufi precipitated mainly in the form of its oxidation product isdissolved. The dyestuii is then transformed into the hydroazine by theaddition of a reducing agent, such as for instance crude carbolic acid,and finally the sulphuric acid solution is poured into water and theprecipitate is worked up as usual.

Example 2 Example 3 10 parts of the dyestuff obtainable according to theU. S. Patent No. 746,784, but while increasing the duration of thealkali fusion to 4 hours, are stirred into parts of concentratedsulphuric acid of 66 Baum. Then at a temperature of about 30 C. 5 partsof water are added, and

manganese dioxide in 100 parts of sulphuric acid 'Of 63 Baum is added.The whole is then warmed up to 70 C. and is stirred for 5 hours at thistemperature. The dyestutf which is obtained in the form of the azine isconverted into N-dihydro- 1.2.1.2-anthraquinoneazine by reduction, andthe product is practically equal in its properties to the dyestuff Adescribed in the U. S. Patent No. 724,789 as regards the purity of itsdyeings.

In a similar manner, for example, a dyestuff obtained according to thecopending application Ser. No. 229,258, now Patent No. 1,790,109 and inparticular according to Example 3 thereof can with advantage be furtherworked up, in which case it is preferable to lengthen the duration ofthe alkali fusion to several hours.

A similar result is obtained when natural manganese dioxide is employedinstead of artificial manganese dioxide.

Example 4 20 parts of 3.3-dimethyl-N-dihydro-1.2.1'.2'-anthraquinoneazine are dissolved in 400 parts of sulphuricacid of 65Baum. Then a suspension of 80 parts of manganese dioxide in 400 parts ofsulphuric acid of 65 Baum, which has been prepared at a temperaturebelow 50 C. is allowed to flow in. The whole is then slowly heated tofrom 70 to 80? C., and is kept at this temperature until no furtherchange in color of a dyed sample occurs. The sulphuric acid solution isthen slowly poured into 3000 parts of water, 300 parts of a solution ofsodium bisulphite of from 38.8 to 39.9 Be. are then poured in, and thewhole is then filtered, washed until neutral and made into a paste. Thedyestuif obtained dyes in shades which are much more green and muchfaster to chlorine than those of the initial material.

The process may also be carried out in concentrated sulphuric acid.

Example 5 40 parts of Indanthrene blue (Colour Index, 1924, N0. 1107)are introduced into a solution of 10 parts of anhydrous boric acid in400 parts of sulphuric acid monohydrate and the mixture is heated to 90C. and kept'at this temperature until a sample poured into water givesdyeings on cot ton which have the desired greenish blue shade. The wholeis then allowed to cool to about 40 C. and 40 parts of water are allowedto flow'in. A suspension of 20 parts of native pyrolusite containingabout 90 per cent of MnOz in 100 parts of sulphuric acid of 66 Baum isthen added. The whole is then stirred for from 4 to 6 hours at 60 C.until no further purification occurs. The dyestuff can then be worked upin the usual manner by pouring it into water and filtering. The dyestuffobtained is in the form of a greenish yellow paste, that is in the formof the azine.

If it is desired to obtain the dyestuff as a blue paste, that is. as theN-dihydroazine, this is effected by treating the reaction mixture with320 parts of oleum having an SOa content of 23 per cent instead ofpouring it into water as already described so that the partly separatedazine goes into solution. Then in order to convert the azine, which isnow mostly in solution, into the dihydroazine, a suflicient quantity ofa reducing agent, for example crude carbolic acid, is added, so that asample poured into water produces a clear blue paste. bolic acid, forexample, are necessary. a The sulphuric acid solution is poured intowater and worked up in the usual manner. The dyestuif obtained dyescotton very clear greenish-blue shades which are fairly fast tochlorine.

Example 6 10 parts of N'dihydro-1.2.1'.2-anthraquinoneazine which, asregards its purity, corresponds to the commercial Indanthrene blue RS,are introduced at from 30 to 40 C. into a solution of 10 parts ofanhydrous boric acid in 150 parts of sulphuric acid monohydrate and thewhole is heated at about 120 C. until a sample taken out is for the mostpart soluble in a from 20 to 25 per cent aqueous solution of pyridine,which is usually the case after about 4 hours. The whole is then cooledto about 30 C. and 8 parts of water and then a suspension of 5 parts offinely ground pyrolusite in 25 parts of concentrated sulphuric acid areallowed to flow in, the whole being then heated to 55 C. and. stirred atfrom 55 to 60 C. until no further improvement in the fastness tochlorine of the dyeings from a sample taken out and worked up can bedetected. This is usually the case after about 5 hours. The whole isthen diluted with 100 parts of con- About 10 parts of crude car-'dyeings on cotton obtained from a warm hydrosulphite vat of the productare greenish blue and when treated with chlorine they only show a slightchange to blue green.

Example 7 10 parts of pure N-dihydro-1.2.1'.2'-anthraquinoneazine fastto chlorine, prepared for example according to Example 4 of the U. S.Patent No. 1,541,156, are introduced into a solution of 10 parts ofanhydrous boric acid in 150 parts of sulphuric acid monohydrate at atemperature of from 30 to 40 C. and the whole is heated to 120 C. whilestirring well. The whole is then stirred at this temperature until asample taken out dissolves almost entirely in a from 20 to 25 per centaqueous solution of pyridine, which is usually the case after about from4 to 5 hours. 1,500 parts of warm water, at a temperature of 60 C. arethen stirred in and the whole is heated to boiling for a period of fromto 1 hour until the original greenish shade no longer changes to blue.The product is filtered off, washed with warm water and worked up in theusual manner. The dyestufi agrees, as regards all its properties, withthat obtainable according to the foregoing example. 7

Example 8 57.5 parts of the N-dihydro-1.2.1'.2-anthraquinoneazine fastto chlorine obtainable according to Example 4 of the U. S. Patent No.1,541,156, are mixed with 42.5 parts of the sulphonic acid of the samedyestuff obtainable according to Example 6 or '7. This mixture, from awarm hydrosulphite vat, gives on cotton shades having the same fastnessproperties as the greenish blue dyestuff obtainable for example byheating pure N dihydro 1.2.1.2' anthraquinoneazine with sulphuric acidin the presence of boric acid.

Example 9 87.5 parts of pure monochlor-N-dihydro-1.2.1.2-anthraquinoneazine, obtainable for example by acting withhydrogen chloride on a suspension of pure l.2.1'.2-anthraquinoneazine insulphuric acid containing some water at an elevated temperature aremixed with 12.5 parts of the sulphonic acid employed in Example 8. Adyeing on cotton with this mixture from a warm hydrosulphite vatcorresponds approximately to the dyeings obtained according to Example8, but is superior to these as regards fastness to chlorine and soaping.

What I claim is:

The process for the purification of greenish blue to blue vat dyestuffsfast to chlorine which comprises treating an impure substance, selectedfrom the group consisting of N-dihydro- 1.2.1.2'-anthraquinoneazine andits methyl and sulphonic acid derivatives, with manganese dioxide insulphuric acid.

PAUL NAWIASKY.

